In the manufacture of telecommunication wires copper conductors are produced from copper rods and then insulated with plastic or pulp. As the conductors are drawn from the copper rods they are cold-worked and then annealed to acquire proper elongation properties. In the annealing process the conductors, while moving at a speed of from 100 to 10,000 feet per minute, are heated to the required annealing temperature for a requisite period of time. The conductors typically vary in size from 10 to 26 gauge.
Within the annealer the copper conductor is typically advanced over two spaced, conductive rollers that serve as electrodes and then through a quenching bath. The roller-electrodes have a voltage impressed across them so that that portion of the conductor that momentarily spans them conducts an electrical current sufficient to become heated to its annealing temperature. The requisite period of annealing time is provided by conductor line speed control.
During the annealing period it is important that the conductor be at a particular temperature or at least within a narrow temperature range. If the conductor is annealed for an insufficient period of time it assumes an insufficient elongation quality thereby rendering it excessively brittle. Conversely, should its annealing temperature be too great then the conductor becomes excessively soft and the process itself wastes power. Heretofore, the temperature achieved has not been measured but merely increased or decreased as a result of elongation tests conducted on conductors previously annealed in the same annealer. It would be preferable, of course, to automate the annealer in order to maintain the proper temperature or temperature range and thereby avoid manufacturing nonconforming wire and reducing residual scrap.
The annealing temperature of the conductor may be increased by applying more power to it, i.e., by increasing its current flow through an increase in the voltage level cross the roller-electrodes. Voltage control itself is easy to provide. The problem in automating annealers however lies in the lack of an effective way of actually measuring the temperature of the moving conductor. It is necessary to make the temperature measurement in the annealer itself, since annealment is a function of time and temperature, before the conductor has had time to cool significantly in order to achieve an accuracy of measurement not dependent upon changes in ambient temperature. However, within the annealer the moving conductor tends to wobble or gyrate as it advances between the roller-electrodes. Temperature measuring devices of the direct contact type cannot be practically employed in this environment since the implantation of thermocouplers on a moving wire carrying high current is not feasible, other than for experimental purposes, and the routing of a gyrating wire against a stationary sensor such as a thermocouple wheel produces inaccurate results due to changes in angle of attack and contact area.
There are noncontact type temperature sensors available for measuring the temperature of moving, elongated materials such as electrically conductive wires. For example, infrared detectors can be employed to measure the temperature of moving objects. Thus, in U.S. Pat. No. 4,081,680 an infrared radiation burglar detector is employed to sense the presence of a human as it walks by the detector. This is done with a combination of housing ports and reflectors in which the infrared detector is mounted so as to sense the movement of the infrared energy radiating human source. U.S. Pat. No. 4,318,089 describes a similar system that uses a plurality of reflective surfaces and infrared sensors to produce a sequence of signals to trigger an alarm. U.S. Pat. No. 4,290,182, which is assigned to the assignee of the present invention, employs an infrared pyrometer for measuring the temperature of continuously moving strand material such as small gauge wire. This is done by positioning the article within a radiation absorbing cone and measuring the thermal radiation emitted from the article with a thermoradiation measuring device positioned proximate to the base of the cone. This technique substantially improves the repeatability of the temperature measurement by shielding the measuring device from stray radiation as well as substantially eliminating reflecting radiation from the article. While this device is useful in measuring conductor temperature after a conductor has been annealed, it is not as suitable in measuring the temperature within the annealer itself where the wire is at a much elevated temperature and is therefore softer and subject to wobbling.
Another pyrometric technique is disclosed in U.S. Pat. No. 3,924,469. Here, a continuously moving wire is passed through a cylindrical, metallic body having a reflective inner surface. A rotating mirror within the cylinder alternately directs the radiation from the heated wire and the reflected radiation from the cylinder walls to a pyrometer. The difference between the direct radiation and reflected radiation provides an indication of the wire temperature. Once again this type of device is not suited for measuring the temperature of a wobbling or gyrating wire.
It thus is seen that a need remains for a method and apparatus for measuring the temperature of a moving elongated article that tends to wobble or gyrate randomly about a preselected path of travel, and for the use of of such particularly in the annealment of conductive wires. It is to this task to which the present invention is primarily directed.